Circuit-arrangement comprising means for the periodic interruption of a current supplied to an inductance coil



p 3, 1957 P J H. JANSSEN I 2,305,384

CIRCUIT-ARRANGEMENT COMPRISING MEANS FOR THE PERIODIC INTERRUPTION OF A CURRENT SUPPLIED TO AN INDUCTANCE COIL Filed NOV. 26, 1952 INVENTOR 7 PETER JOHANNES' HUBERTUS JANSSEN BY AGENT In orderthat the invention may be readily carried into United States atenrOfiFi e 2,805,384

P n e The positive terminal of battery 4 is further connected 2,805,384 to the anode of a diode 10, the cathode of which is con- CIRCUIT.AR ANGEME CO S G MEANS nected toa point 11 of winding 2.. Connected between FOR THE PERIODIC INTERRUPTION OF A CUR- points 12 and 13 of winding 2 is a coil 14 which serves RENT SUPPLIED TO AN INDUCTANCE COIL 5 as a deflection coil foracathode-ray tube.

3; g gg ggz ig ggg 532: 3 5?i flffa igfifij scribed, which serves to produce a saw tooth deflection ican Philips Company Inc. New York, N. Y a cop current through coil 14 and, moreover, the high supply The operation of the circuit-arrangement so far de-l Duration of Delaware directvoltage for a cathode-ray tube, is generally known per se. A Application November 26, 1952, Serial No. 322,622 To the 1 grid circuit ofltubeil is applied a Claimslpriority, application N th l ooth voltage 15 exhibiting a negative voltage pulse December 19, 1951 durlrig the-flyback.

. During the up-stroke of the voltage 15, the wlndlng 2 1 Claim- 15 is traversed by a current increasing substantially linearly with the time. During at least part of the up-stroke the diode 10 is conductive with the result that the capacitor 3 is charged with the polarity indicated in Fig. 1, so that This invention relates to circuit-arrangements for the periodic interruption of a current supplied to an inductance coil, wherein the voltage set up across the coil upon interruption of the current is supplied through a transformer to a load circuit.

Known circuit-arrangements of this type suffer from the disadvantage that disturbing oscillations occur after any interruption of said current. For example, these disturbances may be troublesome in television receiver circuits, where the load circuit is a rectifying circuit producing the high direct voltage required for supplying the cathode-ray tube of the receiver. If the deflection current for the deflection coils of the cathode-ray is also taken from said circuit-arrangement the disturbing oscillations referred to also appear in the deflection circuit and impair the reproduction of the television receiver. If the number of turns of the secondary winding of the transformer is increased to raise the supply direct voltage, the influence of the disturbing oscillations is found to increase accordingly. This is due to the increasing influence of the leakage inductance of the transformer with an increase in the number of turns of the secondary winding.

It has hitherto been sought to minimize said leakage inductance but this does not achieve the desired effect,

i. e., suppression of the disturbing oscillations.

The circuit-arrangement according to the invention is based on the recognition that it is not necessary to 1ninimize the leakage inductance, since, in contradistinction thereto, substantially no disturbing oscillations occur at a very particular value of the leakage inductance.

The circuit-arrangement according to the invention. has the feature that the leakage inductance of the trans-- former is chosen such that both at the instant of interruption and at the instant of completion of the supply circuit the current through the leakage inductance and the derivative of said current are zero.

battery 4 in the anode circuit of tube 1. The deflection coil 14 is traversed by a current increasing substantially linearly with the time; -At the completion of the upstroke the current supplied to coil 2 is cut off, because the negative pulse v16 at the control-grid of tube 1 interrupts 2 there is produced a high pulse voltage pulse, which induces a high voltage pulse in the secondary winding 6, the diode 7 then becoming conductive and a high direct voltagebeing produced across the parallel-connection of capacitor 8 and resistor 9.

Unless special precautionsibe taken it is found that after the flyback a disturbing oscillation appears in the said oscillation being occasioned bythe leakage inductance of the transformer.

With reference to Fig. 2, which is an equivalent diagram and shown in Fig. 1, it will be explained how this disturbing oscillation can be reduced or suppressed.

In the diagram shown in Fig. 2 all vital elements of the circuit-arrangement are imagined to be transformed to the primary side of the transformer. L1 represents the parallel-connection of the transformed self-inductance of deflection coil 14 and the self-inductance of the transformer. This self-inductance L1 will hereinafter be referred to as the transformer inductance.

former windings, of coil 14, of diode 1t and of tube 1 and also of their wiring capacities. The capacity C1 will hereinafter be referred to as the transformer capacity.

the natural self-inductance L0 of the transformer. L2 represents the transformed leakage inductance of the transformer. C2 represents the equivalent capacity of diode 7, the wiring capacity and the capacity of the smoothing capacitor -8, the latter capacity being practically not instrumental in this respect. Said capacity C2 will effect, it will now be described in detail with reference to the accompanying drawing, wherein:

Fig. 1 illustrates schematically one embodiment of a circuit in accordance with the invention; and

2 is a circuit serving t0 assist in the explanation hereinafter be referred to as the capacity of the load of the theory underlying the invention. 0 i it "Th F ll -fl shown in g 1 Comprises an The equivalent diagram further comprises a switch S1 electron discharge tube 1, the anode circuit of which comd a source f t ti l E 11 prises the series-connection of an inductance coil 2, a At the instant t-O corresponding to the beginning of capacitor 3 and an anode supply 4- the flyback of the current through coil 2, switch S1 opens,

The inductance coil 2 constitutes the primary of a i. e., that in the circuit-arrangement shown in Fig. 1, transformer 5 having a secondary 6. This secondary 6 tube 1 is cut-off, the switch S1 closing again at the instant is at one end connected to the upper electrode of catzr corresponding to the completion of the flyback. pacitor 3 and at the other end connected to the anode of If the occurrence of oscillations in the series-connection a diode 7, the cathode of which is connected to ground of the leakage inductance L2 and capacitor C2 of the by way of a filter capacitor 8. The load, for example, load circuit is to be avoided after the instant t=1- it is a cathode-ray tube, represented for convenience by a necessary, both before the instant t=0 and before the resistor 9, is connected in parallel with capacitor 8. instant I='r, to satisfy the conditions that the voltage the .voltagethrough the capacitor. supports the action of.

the anode current of this tube. Consequently across coil transformer and the deflection coil 14 coupled thereto, f

of the part of the circuit-arrangement so far described C1 represents the sum of all capacities of the transv It will beevident that in the absence of coil 14, forexample, the transformer inductance is made up only'of" through capacitor C2 corresponds to the voltage E1, that the current i through the leakage inductance L2 is zero at said instants and that the derivative of said current is also zero. Theseconditions make, it

possible to establish the necessity of very definitevalues holding for the ratio of the two parallel resonance frequencies a and ,9 of the circuit comprisingthe three parallel circuits shown in Fig. 2.

The condition which is optimum for other reasons is given by the relation:

where z represents the ratio between the timeof interruption (*r) and theduration of the period.

As stated above, there are still other values for at which no or substantially no disturbing oscillations occur, for example, if:

If, for example, z=0.15 as is often the case in television, the optimum value is When further elaborating the last-mentioned-condition for a it is found that if 2L -17 and 1--q the expression l()pq= (pc,1} p-ll) must be satisfied;

Hence, if the value of the inductance of transformer L1 is fixed and if this also holds for the capacity of transformer C1 and the capacity of load circuit C2, a correct choice of the value of leakage inductance La permits the desired condition to be fulfilled.

At the given value :2.8 the maximum value:

iL, =r5sarLz B-a where i represents the current through the inductance L1 at the instant t=0, is found for the voltage through capacitor C2.

At the other possible values for practically no disturbing oscillation occurs, it is true, but the maximum value of the voltage through capacitor C2 is much smaller, so that the value 2.8 for 4 is optimum if the circuit-arrangement is used for generating high direct voltages.

If, in accordance with prior art arrangements, the leakage inductance could be macle, very low, i. e., approximately zero, the voltage through capacitor C2 would maximally attain DtiLl. Hence, the use of the circuitarrangement according to the invention, as compared with the solution hitherto considered ideal, yields a. high voltage which is more than a factor 1.5 higher.

With the circuit-arrangement, shown in Fig, 1, the

correct proportions are obtained by a judicious-choice of the coupling factor of the transformer and the values of the self-inductance and capacity of the transformer and. also of the capacity of the load circuit;

It will, however, often be preferred to make the coupling factor of the transformer variable in order that it may be adjusted to the correct' value, for example, in

. the manufacture of television apparatus. a

One embodiment of such a solution is shown in'Fig. l, in which an additional coupling circuit comprising an inductance coil having an adjustable inductance value is provided between the primary and the secondary of transformer 5. To this, end a connector comprising the variable inductanct coil 19 is provided between point 17 of the primary 2 and point 18 of the secondary 6.

The correct coupling factor and consequently the correct value of the leakage inductance of the transformer are. obtained by correct setting of the value of the in:

ductance of coil 19.

It will be obvious that instead of using tappings on the transformer windings, the coupling circuit may be obtained by means of additional windings coupled to the 1 primary and the secondary of the transformer respectively.

While I have thus described my invention with specific examples and embodiments thereof, other modifications will be readily apparent tov thoseskilled in the.

art without departing from the spirit and the scope of;

, the inventions as defined in the appended claim.

What I, claim is: A television circuit arrangement comprising a transformer having a primary coil and a secondary coil, a

two-terminal source of operating voltage, a load circuit including a rectifier connected to said secondary coil, a capacitor connected'between one end. of said primary coil and one of said terminals, means connected to supply a periodically interrupted, current flow in said primary coil, a rectifier connected between a point on said primary coil and said' one terminal of the source. of operating voltage, a deflection coil connected between two points on said primary coil, and an inductor-connected between a pomt on said primary coil and a point on said secondary coil.

References Cited in the file'of this patent 

